The present invention relates to a catalyst for homo- or co-polymerization of ethylene, or more particularly to a solid titanium catalyst supported on a magnesium-containing carrier, having high catalytic activity and excellent polymerization properties, which can provide polymers of high bulk density and reduce the amount of polymers soluble in a medium during polymerization.
Magnesium-containing catalysts for preparation of an ethylene polymer or copolymer are known to have a high catalytic activity and to be instrumental in production of polymers having a high bulk density. They are also known to be suitable for both liquid and gaseous phase polymerization alike. By the liquid phase ethylene polymerization is meant the polymerization reaction performed of bulk ethylene or in such media as isopentane and hexane, while the features important for the catalyst used in such polymerizations are high catalytic activity, the resultant polymer""s high bulk density, etc. Apart from these, a salient variable to decide the quality of a catalyst, especially its commercial usefulness, is how much polymer remains soluble in the medium.
Many catalysts based on magnesium titanium along with the processes of their production have been reported. Uses of a magnesium solution intended to obtain a catalyst for polymerization of olefin having a high bulk density have also been learned. There are ways of obtaining magnesium solutions by means of reacting magnesium compounds with such electron donors as alcohol, amine, cyclic ether, organic carboxylic acid, etc, in the presence of hydrocarbon solvents. Of which, instances of using alcohol are disclosed in U.S. Pat. Nos. 4,330,649 and 5,106,807. A way of preparation of a magnesium-carrying catalyst by reacting a magnesium solution with such a halogen-containing compound as titanium tetrachloride is also well known. Attempts have been made by addition thereto of ester compounds to adjust the catalytic activity and the resultant polymer""s molecular weight distribution. Such catalysts provide high bulk density of polymer, but have much yet to be improved in the aspects of the catalytic activity and the produced polymer""s molecular weight distribution. Tetrahydrofuran, a cyclic ether, is in use as solvent for magnesium compounds in U.S. Pat. Nos. 4,777,639 and 4,518,706.
U.S. Pat. Nos. 4,847,227, 4,816,433, 4,829,037, 4,970,186, and 5,130,284 have disclosed processes for producing catalysts of excellent activity for polymerization of olefin having a high bulk density by reacting titanium chlorides with such electron donors as magnesium alkoxide, dialkyl phthalate, phthaloyl chloride, etc.
U.S. Pat. No. 5,459,116 has reported a process for preparation of a titanium-carrying solid catalyst by contact-reacting a magnesium solution containing, as electron donor, an ester having at least one hydroxy group with a titanium compound. Such processes make it possible to obtain a catalyst with a high catalytic activity, ensuring the produced polymer a high bulk density, but co-polymerization aspects have not been paid due heed.
As can be seen from the above, It is desirable that catalysts be developed for homo-and co-polymerization of ethylene that are simple in their production processes, yet have a high catalytic activity, and provide the produced polymers with a high bulk density, and give reduced soluble polymer left behind in the medium in slurry polymerization.
Hence the present invention, wherein it has been made possible to produce a catalyst of high activity from low-priced materials by means of a simple industrial process, the said catalyst being instrumental in preparation of polymers having a high bulk density and with less polymeric constituents soluble in the medium after the reaction. The actual steps and processes for production of the catalyst revealed in the present embodiment have never before been known in any existing patents or literature.
The present embodiment provides a solid catalyst of high catalytic activity for homo- and co-polymerization of ethylene, ensuring the polymer produced by the use of the catalyst with a high bulk density and excellent polymerization activity as well as reduced polymeric material to remain soluble in the medium.
The present embodiment also provides a method, simple yet practical, for producing the said solid catalyst.
The solid titanium catalyst, described herein, for homo- and co-polymerization of ethylene, excellent in catalytic activity and instrumental in production of polymers with a high bulk density and less polymer soluble in the medium, is produced by a simple yet effective process comprising Step (i) of producing a magnesium solution by contact-reacting a halogenated magnesium compound and alcohol, Step (ii) of reacting the solution with a phosphorus compound and an ester compound having at least one hydroxy group, and Step (iii) of adding thereto a mixture of a titanium compound and a silicon compound.
The kinds of halogenated magnesium compounds usable include such dihalogenated magnesiums as magnesium chloride, magnesium iodide, magnesium fluoride, and magnesium bromide; such alkylmagnesium halides as methylmagnesium halide, ethylmagnesium halide, propylmagnesium halide, butylmagnesium halide, isobutylmagnesium halide, hexylmagnesium halide, and amylmagnesium halide; such alkoxymagnesium halides as methoxymagnesium halide, ethoxymagnesium halide, isopropoxymagnesium halide, butoxymagnseium halide, and octoxymagnesium halide; and such an aryloxymagnesium halide as phenoxymagnesium halide or methylphenoxymagnesium halide. A mixture of two or more of these compounds can also be used. These magnesium compounds may be effective when they are used in the form of a complex with other metals.
The above-listed halogenated magnesium compounds may be represented by simple chemical formulae, but exceptions may arise from differences in the methods of their production. In such exceptional cases they generally can be regarded as mixtures of these listed magnesium compounds. For instance, the compounds obtained by reacting a magnesium compound with a polysiloxane compound, a halogen-containing silane compound, ester, or alcohol; the compounds obtained by reacting a magnesium metal with alcohol, phenol, or ether in the presence of halosilane, phosphorus pentachloride, or thionyl chloride may also be used. The preferable magnesium compounds are magnesium halides, especially magnesium chloride and alkylmagnesium chloride, preferably those that have C1xcx9cC10 alkyl groups; alkoxymagnesium chlorides, preferably those that have C1xcx9cC10 alkoxy groups; and aryloxy magnesium chlorides and preferably those that have C6xcx9cC20 aryloxy groups.
The magnesium solution may be produced with the aforesaid magnesium compounds by the use of an alcohol solvent in the presence or absence of a hydrocarbon solvent.
The kinds of hydrocarbon solvents which may be used for this purpose include, for instance, such aliphatic hydrocarbons as pentane, hexane, heptane, octane, decane, and kerosene; such alicyclic hydrocarbons as cyclobenzene, methylcyclobenzene, cyclohexane, and methylcyclohexane; such aromatic hydrocarbons as benzene, toluene, xylene, ethylbenzene, cumene, and cymene; and such halogenated hydrocarbons as dichloropropane, dichloroethylene, trichloroethylene, carbon tetrachloride, and chlorobenzene.
When a magnesium compound is turned into a solution, alcohol is used in the presence of any of the above-listed hydrocarbons. The kinds of alcohols used for this purpose include, for instance, such an alcohol, which contains from 1xcx9c20 carbons as methanol, ethanol, propanol, butanol, pentanol, hexanol, octanol, decanol, dodecanol, octadecylalcohol, benzylalcohol, phenylethylalcohol, isopropylbenzylalcohol, and cumyl alcohol. Of these, the preferable is such an alcohol which contains 1xcx9c12 carbons. The desired average size and distribution of particles of the catalyst may vary according to the kinds and total quantity of alcohol, the kinds of magnesium compounds, the ratio of magnesium to alcohol, etc., but the total quantity of alcohol to obtain the magnesium solution is at least 0.5mol to one mol of the magnesium compound, preferably about 1.0 molxcx9c20 mols, and more preferably about 2.0 molsxcx9c20 mols.
The reaction of a magnesium compound with alcohol, in preparation of the solution, is preferably performed in a hydrocarbon medium, at the reaction temperature, though dependent upon the kinds and quantity of the alcohol, of about xe2x88x9225xc2x0 C., preferably xe2x88x9210xc2x0 C.xcx9c200xc2x0 C., and still more preferably about 0xc2x0 C.xcx9c150xc2x0 C., The reaction preferably continues for about 30 minutes to four hours.
The phosphorus compound used as an electron donor in preparation of the catalyst is represented by the following general formula:
PXaR1b(OR2)c, or
POXdR3e(OR4)f.
Here xe2x80x9cXxe2x80x9d is halogen atom or atoms; R1, R2, R3, and R4 are independently hydrocarbons having 1xcx9c20 carbons, for example alkyl, alkenyl, aryl groups, etc., and with a+b+c=3, 0xe2x89xa6axe2x89xa63, 0xe2x89xa6bxe2x89xa63, 0xe2x89xa6cxe2x89xa63; d+e+f+3, 0xe2x89xa6dxe2x89xa63, 0xe2x89xa6exe2x89xa63, 0xe2x89xa6fxe2x89xa63.
Actual examples of these include phosphorus tribromide, diethylchlorophosphite, diphenylchlorophosphite, diethylbromophosphite, diphenylbromophosphite, dimethylchlorophosphite, phenylchlorophosphite, trimethylphosphite, triethylphosphite, tri-n-bu-tylphosphite, trioctylphosphite, tridecylphosphite, triphenylphosphite, triethylphosphite, tri-n-butylphosphate, triphenylphosphate, etc., and, besides these, other phosphorus compounds, if they satisfy the above formula, can also be used. The quantity of these for use is adequately something below 0.25 mol to a mol of the magnesium compound, and more preferably 0.2 mol.
The ester compound containing at least one hydroxy group for use as another electron donor in the production of the catalyst may include, for example: such unsaturated aliphatic acid esters containing at least one hydroxy group as 2-hydroxy ethylacrylate, 2-hydroxy ethylmethacrylate, 2-hydroxy propylacrylate, 2-hydroxy propylmethacrylate, 4-hydroxy butylacrylate, and pentaerythritol triacrylate; such aliphatic monoesters or polyesters containing at least one hydroxy group as 2-hydroxy ethylacetate, methyl 3-hydroxy butylate, ethyl 3-hydroxy butylate, methyl 2-hydroxy isobutylate, ethyl 2-hydoxy isobutylate, methyl-3-hydroxy-2-methyl propionate, 2,2-di-methyl-3-hydroxy propionate, ethyl-6-hydroxy hexanoate, t-butyl-2-hydroxy isobutylate, diethyl-3-hydroxy glutarate, ethyl lactate, isopropyl lactate, butylisobutyl lactate, isobutyl lactate, ethylmandelate, dimethyl ethyl tartrate, ethyl tartrate, dibutyl tartrate, diethyl citrate, triethyl citrate, ethyl 2-hydroxy caproate, and diethyl bis-(hydroxy methyl) malonate; such aromatic esters containing at least one hydroxy group as 2-hydroxy ethyl benzoate, 2-hydroxy ethyl salicylate, methyl 4-(hydroxy methyl) benzoate, methyl 4hydroxy benzoate, ethyl 3-hydroxy benzoate, 4-methyl salicylate, ethyl salicylate, phenyl salicylate, propyl 4-hydroxy benzoate, phenyl 3-hydroxy naphthanoate, monoethylene glycol monobenzoate, diethylene glycol monobenzoate, and triethylene glycol monobenzoate; and such alicyclic esters containing at least one hydroxy group as hydroxy butyl lactone. The quantity of such an ester compound containing at least one hydroxy group should be 0.001 molxcx9c5 mols to a mol of the magnesium, and preferably 0.01 molxcx9c2 mols. The quantity of these should preferably be 0.05 molxcx9c3 mols to one mol of the magnesium, and more preferably 0.1 molxcx9c2 mols.
The temperature for the contact-reaction of the magnesium compound solution with a phosphorus compound and an ester compound containing at least one hydroxy group is adequately 0xc2x0 C.xcx9c100xc2x0 C., and more preferably 10xc2x0 C.xcx9c70xc2x0 C.
The magnesium compound solution which has been reacted with an ester compound containing at least one hydroxy group and a phosphorus compound is reacted with a mixture of a liquid titanium compound represented by the general formula Ti(OR)aX4xe2x88x92a (xe2x80x9cRxe2x80x9d is a hydrocarbon group, xe2x80x9cXxe2x80x9d a halogen atom, and xe2x80x9caxe2x80x9d a natural number from 0 to 4) and a silicon compound represented by the general formula RnSiCl4xe2x88x92n (xe2x80x9cRxe2x80x9d is hydrogen; an alkyl, alkoxy, haloalkyl, or aryl group having 1xcx9c10 carbons; or a halosillyl or halosillylalkyl group having 1xcx9c8 carbons, and xe2x80x9cnxe2x80x9d is a natural number from 0 to 3), for crystallization of the particles of the catalyst.
The kinds of titanium compounds which satisfy the above general formula Ti(OR)aX4xe2x88x92a include, for example, such tetrahalogenated titaniums as TiCl4, TiBr4, and TiI4; such trihalogenated alkoxytitaniums as Ti(OCH3)Cl3, Ti(OC2H5)Cl3, Ti(OC2H5)Br3, and Ti(O(i-C4H3)Br3; such dihalogenated alkoxy titaniums as Ti(OCH3)2Cl2, Ti(OC2H5)2Cl2. Ti(O(i-C4H9))2Cl2, or Ti(OC2H5)2Br2; and such tetraalkoxy titaniums as Ti(OCH3)4, Ti(OC2H5)4, and Ti(OC4H9)4. Mixtures of the above titanium compounds may also be used. The preferable titanium compounds are halogen-containing compounds, and more preferably tetrachlorides of titanium.
The silicon compounds which satisfy the above general formula RnSiCl4xe2x88x92n include, for example, silicon tetrachloride; such trichlorosilanes as methyltrichlorosilane, ethyltrichlorosilane, and phenyltrichlorosilane; such dichlorosilanes as dimethyldichlorosilane, diethyldichlorosilane, diphenyldichlorosilane, and methylphenyldichlorosilane; and such monochloorsilanes as trimethylchlorosilane. The mixtures of these silicon compounds can also be used. The preferable silicon compound is silicon tetrachloride.
The quantity of the mixture of titanium and silicon compounds used in crystallization of the magnesium compound solution is adequately 0.1 molxcx9c200 mols to a mol of the magnesium compound, preferably 0.1 molxcx9c100 mols, and still more preferably 0.2 molxcx9c80 mols. The molar ratio of titanium compound to silicon compound is adequately 1:0.05xcx9c0.95, preferably 1:0.1xcx9c0.8.
The shape and size of the solid matter crystallized by reaction of the magnesium compound solution with the mixture of titanium and silicon compounds greatly vary, dependant upon the reaction conditions. Therefore it is advisable to carry out the reaction at a sufficiently low temperature for formation of the solid constituents. Preferably, it is better to carry out a contact reaction at xe2x88x9270xc2x0 C.xcx9c70xc2x0 C., and more profitably at xe2x88x9250xc2x0 C.xcx9c50xc2x0C. After the contact reaction the temperature is slowly raised and it is left at 50xc2x0C.xcx9c150xc2x0 C. for 0.5 hour to five hours for sufficient reaction.
The solid particles obtained by the above-said reaction can be further reacted with a titanium compound. The titanium compound, which can be used for this purpose, is a titanium halide or a halogenated alkoxy titanium having 1 to 20 carbons in the alkoxy group. In some cases mixtures of these may also be used. Of these, the preferable is a titanium halide or a halogenated alkoxy titanium having one to eight carbons in the alkoxy group, and still more preferable is a titanium tetrahalide.
The solid titanium catalyst produced by the method provided herein is profitably used in homo- and co-polymerization of ethylene. This catalyst is especially preferably used in polymerization of ethylene and also in co-polymerization of ethylene with such xcex1-olefins containing three or more carbons as propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, and 1-hexene.
The polymerization reaction in the presence of the catalyst is performed with the use of (a) the solid titanium catalyst consisting of magnesium, titanium, halogen and an electron donor, and (b) a catalyst system consisting of compounds of the organometals of Groups 2, 12, or 13 on the periodic table of elements.
The solid complex titanium catalyst (a) can also be pre-polymerized in ethylene or xcex1-olefin, prior to use as constituent in a polymerization reaction. The pre-polymerization can be performed in the presence of a hydrocarbon solvent like hexane at a sufficiently low temperature and under the law pressure conditions of ethylene or xcex1-olefin in the presence of the aforesaid catalyst constituents and such an organic aluminum compound as triethylaluminum. Pre-polymerization makes catalyst particles wrapped in polymers to maintain the shape of the catalyst and thus helps to better the shape of the polymer after polymerization. The ratio in weight of polymer to catalyst after the pre-polymerization is usually 0.1:1xcx9c20:1.
The organometal compound (b) can be represented by the general formula: MRn. Here xe2x80x9cMxe2x80x9d is a metal of Groups 2, 12, or 13 on the periodic table of elements, such as magnesium, calcium, zinc, boron, aluminum or gallium; xe2x80x9cRxe2x80x9d is an alkyl group having 1 to 20 carbons, such as methyl, ethyl, butyl, hexyl, octyl, or decyl; and xe2x80x9cnxe2x80x9d is the valence of the metal atom. For the more preferable organic metal compounds such trialkylaluminums containing an alkyl group of one to six carbons as triethylaluminum and triisobutylaluminum. Their mixtures are also commendable. In some cases such organic aluminum compounds containing one or more halogen or hydride groups as ethylaluminum dichloride, diethylaluminum chloride, ethylaluminum sesquichloride, or diisobutylaluminum hydride may be used.
The polymerization reaction may be performed in gaseous phase, in bulk in the absence of an organic solvent, or in a liquid slurry in the presence of an organic solvent. The reactions, however, are performed in the absence of oxygen, water, or any compounds that may act as catalytic poison.
In the case of liquid slurry polymerization, the preferable concentration of the solid complex catalyst, is about 0.00 Mmolxcx9c5 Mmols, more preferably about 0.001 molxcx9c0.5 Mmols in terms of the number of titanium atoms in the catalyst to a liter of the solvent. For the solvent, such alkanes or cycloalkanes as pentane, hexene, heptane, n-octane, isooctane, cyclohexene, and methylcyclohexene, such alkylaromatics as toluene, xylene, ethylbenzene, isopropylbenzene, ethyltoluene, n-propylbenzene, and diethylbenzene, such halogenated aromatics as chlorobenzene, chloronaphthalene, and orthodichlorobenzene; and mixtures of these, are useful.
In the case of gaseous polymerization the quantity of the solid complex titanium catalyst (a) is about 0.001 Mmolxcx9c5 Mmols, preferably about 0.001 Mmolxcx9c1.0 Mmols, still more preferably about 0.01 Mmolxcx9c0.5 Mmols in terms of the number of titanium atoms to a liter of polymerization reaction volume.
The preferable concentration of the organometal compound (b) is about 1 molxcx9c2,000 mols, more preferably about 5 molsxcx9c500 mols, in terms of the number of the atoms of the organometal to a mol of the titanium atoms in the catalyst (a).
To secure a high speed in polymerization the reaction is performed at a sufficiently high temperature regardless of the polymerization process. Generally, about 20xc2x0 C.xcx9c200xc2x0 C. are adequate, and more preferably 20xc2x0 C.xcx9c95xc2x0 C. The pressure of a monomer at the time of polymerization is adequately 1xcx9c100 atm, and more preferably 2xcx9c50 atm.
In the present invention, the molecular weight is expressed as a melt index (MI) (ASTM D1238), which is generally known in the art. The value of MI generally becomes greater as the molecular weight decreases.
The products obtained with the use of the catalyst are an ethylene polymer or copolymers of ethylene with xcex1-olefin, having an excellent bulk density and fluidity. The yield of polymers is sufficiently high, requiring therefore no further process for removal of the residue of the catalyst.
Embodiment
The present invention is described in further detail below, through embodiment examples and comparative examples. The present invention is not limited to these examples.